There are many kinds of doors such as gates installed outdoors, and living room doors and furniture doors installed indoors.
Generally, the conventional doors are constituted such that: the solid peripheral frame members are joined together in the form of " , " and a plywood is fitted to the frame of the door. However, this conventional door has disadvantages such that: the joined portions of the frame are easily damaged, and it is impossible to inscribe exquisite patterns.
However, recently, in an attempt to overcome the above described disadvantages, there has appeared a door made of a plurality of laminas and having the same structure as the solid wood doors, and this door has been put to the practical use.
The manufacturing process for this door will be briefly described. That is, a sufficiently dried wood is cut into laminas of a cetain thickness, and a strong adhesive is spread on the surfaces of the laminas. The laminas are then assembled and pressed by a high power press before finishing. Thus, doors of various kinds can be manufactured.
Disadvantages occur when rectangular laminas are simply put together to form a door as described above for example, twisting and other deformations can occur during use; the weight of the door is also increased.
As shown in FIG. 11, pipes 10 can be buried into the upper and lower portions of the door to prevent twisting and other deformation. However, in such a case, not only the manufacturing process becomes complicated, but also the door can produce cracks upon receipt of impacts.